by Abigail Van Buren

DEAR ABBY: My 13-year-old twin daughters were very close, considered each other their "best friend" and got along beautifully sharing a room. Disagreements and arguments were rare and nearly always minor.

However, during the last few months, out of the blue, they have begun fighting and arguing frequently. They scream and yell at each other over the pettiest of things. Instead of being constant companions, they no longer want to do anything together.

Now they spend time separately with friends. They are even asking us to get a bigger house so they can have separate rooms. They refuse to share the bathroom in the morning -- which had never been a problem before -- claiming to need privacy from each other. This makes things very difficult during the morning rush because we also have a 15-year-old son who needs to get ready for school.

I am at my wit's end trying to deal with this. I have no idea what caused this sudden rift, and the girls don't seem to understand it either. Please help. -- LOUISIANA MOM OF 3

DEAR LOUISIANA MOM: What's causing the rift is that your daughters are maturing. Their hormones are changing, and they are trying to become individuals. This is a healthy thing, and you should not worry.

As to the scheduling problem in the bathroom -- if the girls won't cooperate and share the facilities, then they will have to alternate. And your job as mother and referee is to see that they do.

DEAR ABBY: I recently visited my favorite brother and his family for a few days. My sister-in-law invited me to go out for coffee with her -- just the two of us -- then proceeded to tell me in great detail about an affair she had about a year ago. I was floored.

My brother doesn't know about this, and now this information is haunting me. If my brother knew my husband had cheated and didn't tell me, I'd be furious. On the other hand, telling my brother will hurt him. What should I do? -- BURDENED IN CALIFORNIA

DEAR BURDENED: Ask yourself this question -- if you wanted to keep an infidelity from your spouse, would you confide "in great detail" in his sibling? If the answer is no, then consider that your sister-in-law is either completely lacking in judgment or subconsciously aching to get caught. Then follow your conscience.

DEAR ABBY: I would appreciate your opinion on a matter that has me concerned. My son and his wife have gone on a trip to Africa. I am watching the grandchildren part of the time while their parents are gone.

The night before my son left, I said, "To be prudent and prepared in case of emergency, in the event you have an accident, who will be the permanent guardians for these children?" His reply was, "That is none of your business. It is a personal matter."

Was I out of bounds to ask that question? -- GUILT-RIDDEN IN REDMOND, WASH.

DEAR GUILT-RIDDEN: Absolutely not. Your question was a timely and intelligent one. A more pertinent question would now be why your son became defensive that you asked. Could it be that he feels guilty because the answer is you will not be named as guardian?

If that's the case, then some written provision should be made specifying that if anything happens to him and your daughter-in-law, you will have visitation with your grandchildren -- because unless it is on paper, there is no guarantee you will.

Abby shares more than 100 of her favorite recipes in two booklets: "Abby's Favorite Recipes" and "More Favorite Recipes by Dear Abby." Send a business-size, self-addressed envelope, plus check or money order for $12 (U.S. funds)